1. Field of the Invention
The present invention relates to a sweetened foamable oil-in-water emulsion which is distributed and utilized also at ordinary temperatures (from 20 to 35.degree. C.). More particularly, it relates to a sweetened foamable oil-in-water emulsion which is to be whipped up and used as toppings or fillings of cakes, sweet rolls, desserts, etc. and capable of giving a whipped cream improved particularly in the heat resistance and melting behavior in mouth.
2. DISCUSSION OF THE BACKGROUND
There have been developed a number of foamable emulsions (hereinafter sometimes referred to as foamable creams) which are whipped up and used as toppings or fillings of cakes, sweet rolls, desserts, etc. The properties to be required for these foamable creams are varied depending on the form of the product and distribution means (in a chilled state or at ordinary temperatures). Further, the characteristics to be required therefor, for example, whipping characteristics (over-run, whipping time) and physical properties (heat resistance and melting behavior of the whipped cream), are also varied.
As such foamable emulsions, there have been widely used water-in-oil emulsions and oil-in-water ones. Among them, water-in-oil emulsions, of which water activity (Aw) can be regulated to a low level, have been generally utilized since they are required to prolong their shelf lives in summer, when they are distributed at ordinary temperatures throughout the year. However, a water-in-oil emulsion comprises, as the continuous phase, an oily phase containing a fat or oil as the main component, which is generally apt to make the taste oily, whereas today's consumers prefer a fresh taste. In recent years, accordingly, there has been an increase in the demand for an oil-in-water emulsion as a substitute for a water-in-oil emulsion. In particular, it has been urgently required to develop a sweetened oil-in-water emulsion usually containing from 10 to 50% by weight of sugars which can be distributed and used at ordinary temperatures throughout the year. Unsweetened oil-in-water emulsions, which contain no or a little of sugars, are usually handled as a chilled product to be distributed at about 10.degree. C., and sugars are added thereto in the step of whipping.
Examples of the sweetened oil-in-water emulsions include those described in U.S. Pat. Nos. 4,146,652 (published on Mar. 27, 1979), 4,234,611 (published on Nov. 18, 1980) and 4,390,550 (published on Jun. 28, 1983), of which the assignee is RICH PRODUCTS CORP. Properties indispensable to such a sweetened oil-in-water type emulsion as described above include not only fundamental properties, such as an emulsion stability and whipping characteristics, as a foamable emulsion, but also an excellent melting behavior in mouth and a good heat resistance of the whipped cream, that is, even when the whipped cream which is prepared by whipping an oil-in-water type emulsion is stored at ordinary temperatures, in particular, i the summer (about 30.degree. C.) for a long time, it does not undergo loss in shape and separation of water but remains stable.
Oil-in-water emulsions-in the prior art contain a natural animal or vegetable fat (for example, rapeseed oil, soybean oil or those obtained by hardening them to a low extent) as a base fat or oil. There has been known that an extremely hardened product of the above-mentioned natural animal or vegetable fat is blended with the base fat or oil for improving heat resistance of such an oil-in-water emulsion. However, the addition of such a fat or oil generally causes an increase in the amount of fat (or oil) crystals and thus largely deteriorates the taste, e.g., melting behavior in mouth, which is derived from the base fat or oil. Also, attention is paid to the content of fat (or oil) crystals and emulsifiers in view of the improvement of the emulsion stability. Thus, there have been proposed methods for using a specific triglyceride and an emulsifier for improving the heat resistance of a cream prepared by whipping an oil-in-water emulsion. However, the proposed methods cannot give heat resistance at the desired level to a cream but merely make a cream resistant to a temperature of 20 to 25.degree. C. Japanese Patent Publication-A No. 4-88944 (published on Apr. 23, 1992) has proposed an oil-in-water emulsion composition which contains 10% by weight or more and less than 30% by weight of a diglyceride in the oily phase. In this emulsion, a diglyceride containing an unsaturated fatty acid moiety as the fatty acid moiety is mainly used. The reason why such a diglyceride is used is to improve the milky taste and body.